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-   -   Convert grams to moles formula? (https://www.askmehelpdesk.com/showthread.php?t=581909)

  • Jun 14, 2011, 10:19 AM
    nene87
    Convert grams to moles formula?
    How many moles of N are in 0.203g of N2O?
  • Jun 14, 2011, 01:00 PM
    jcaron2
    First you need to figure out how much a mole of N2O weighs. This, by definition, is called the molecular weight. You find it by adding up the atomic weights of each of the constituent atoms. For example, an N2O molecule has two N atoms. Since N has an atomic weight of 14.0067, that means that a mole of N2O molecules contains 2 x 14.0067 = 28.0134 g of N. It also contains a certain mass of oxygen which must be added in to find the molecular weight, but I'll let you look up that value.

    Once you know the mass of a mole of N2O, you can figure out how many moles you have by dividing 0.203g of N2O by the molecular weight you calculated. You should find that you have a little less than 5/1000s of a mole.
  • Jun 15, 2011, 10:32 AM
    Unknown008

    One slight correction in your post Josh :)

    One mole of N2O contains 2 moles of N.

    You have to multiply the answer that you get by 2 after getting it!
  • Jun 15, 2011, 10:56 AM
    jcaron2
    Comment on Unknown008's post
    Isn't that what I said (more or less)? I never outright said there were two moles of N, but I did say there were two atoms per molecule so you have to multiply N's contribution by 2.
  • Jun 15, 2011, 11:06 AM
    Unknown008

    Hm... I'll wait some time before getting back to it, or the actual answer will get over the place while we're trying to sort it out :p
  • Jun 18, 2011, 11:18 AM
    Unknown008

    Okay, the OP seems unwilling to follow up.

    First, we got to find the number of moles of N2O.

    No. of moles of N2O = Mass/Mr = 0.203/(14+14+16) = 0.004613636 mol = 0.00461 mol

    And thus number of moles of N = 2 x 0.00461 = 0.00923 mol

    Now that I'm re-reading though, your post is indeed quite abstract :p
  • Jun 18, 2011, 12:19 PM
    jcaron2

    Ahhh, got it. :o

    As you've probably guessed, I misread the question. Yes, you're right. There are twice as many moles of N as there are of N2O. I read it as "how many moles of N2O".

    This is why YOU are the chemistry expert, not me. :D

    Btw, I'm still unable to rep you until I spread it around a little more.
  • Jun 18, 2011, 12:31 PM
    Unknown008

    It's okay, don't worry :)

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